Digital signal processing based de-serializer

ABSTRACT

A DSP based SERDES performs compensation operations to support high speed de-serialization. A receiver section of the DSP based SERDES includes one or more ADCs and DSPs. The ADC operates to sample (modulated) analog serial data and to produce digitized serial data (digital representation of the modulated analog serial data). The DSP communicatively couples to the ADC and receives the digitized serial data. Based upon the known characteristics of the digitized serial data and the digitized serial data itself, the DSP determines compensation operations to be performed upon the serial data to compensate for inadequacies of the receiver and/or channel response. These compensation operations may be (1) performed on the analog serial data before digitization by the ADC; (2) applied to the ADC to modify the operation of the ADC; and/or (3) performed on the digitized serial data by the DSP or another device.

CROSS REFERENCE TO RELATED PATENTS/PATENT APPLICATIONS ContinuationPriority Claim, 35 U.S.C. §120

The present U.S. Utility patent application claims priority pursuant to35 U.S.C. §120, as a continuation, to the following U.S. Utility patentapplication which is hereby incorporated herein by reference in itsentirety and made part of the present U.S. Utility patent applicationfor all purposes:

1. U.S. Utility application Ser. No. 10/086,267, entitled “DIGITALSIGNAL PROCESSING BASED DE-SERIALIZER,” filed Mar. 1, 2002, now U.S.Pat. No. 7,336,729, which claims priority pursuant to 35 U.S.C. §119(e)to the following U.S. Provisional patent applications which are herebyincorporated herein by reference in their entirety and made part of thepresent U.S. Utility patent application for all purposes:

a. U.S. Provisional Application Ser. No. 60/273,215, entitled“High-speed analog to digital conversion system for communicationsapplications,” filed Mar. 1, 2001, now expired.

b. U.S. Provisional Application Ser. No. 60/290,263, entitled “Digitalsignal processing based transceiver for high-speed interconnections,”filed May 11, 2001, now expired.

Incorporation by Reference

The following U.S. Utility patent applications are hereby incorporatedherein by reference in their entirety and made part of the present U.S.Utility patent application for all purposes:

1. U.S. Utility patent application Ser. No. 09/844,441, entitled,“HIGH-SPEED SERIAL DATA TRANSCEIVER AND RELATED METHODS,” filed Apr. 30,2001, now U.S. Pat. No. 7,058,150, issued on Jun. 6, 2006.

2. U.S. Utility patent application Ser. No. 10/085,071, entitled“METHODS AND SYSTEMS FOR DSP-BASED RECEIVERS,” filed Mar. 1, 2002, nowU.S. Pat. No. 7,245,638, issued on Jul. 17, 2007.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The invention relates generally to de-serialization of serial datastreams; and, more particularly, it relates to digital signal processingbased de-serialization.

2. Description of Related Art

A conventional trend within communications technologies towards tryingto achieve higher and higher operating rates has largely been gearedtowards employing wide parallel bus architectures. These implementationsinherently consume a great deal of real estate. In chip-to-chipapplications, one of the greatest consumers of real estate includes thewide parallel interconnections themselves that enable the communicationand interconnection between the various devices. The constant increasesin complexity and speed of digital hardware has turned the problems ofinterconnecting components increasingly difficult in contexts such aschip-to-chip, connections between multiple circuit boards across backplanes, and other connections having a need for high speed communicationwhile also being constrained by real estate and space.

Moreover, aside from the higher data rates desired in the industry, asthe complexity of chips continues to increase, there is also commonly anassociated requirement to provide a larger number of interconnections.Again, to ensure higher data communication rates, there is often thetrend towards providing broad bus width interconnections between thedevices.

One conventional approach to arrive at these high communication rateswhile also trying to address the design considerations of conservingspace and real estate is to employ high-speed serial interconnections. Asingle high-speed serial interconnection may replace a large number oflower speed interconnections. As a result, a high-speed serialinterconnection is largely more space and real estate conserving thanparallel type interconnections. For this reason, many industries,including the computer and communications industries, have begun the useof high-speed serial transceivers for many applications includingchip-to-chip and board-to-board applications. These transceivers, thatmay be referred to as SERDES (serializer-de-serializer) run at speeds ofseveral hundred Mega-bits per second (Mb/s) to Giga-bits per second(Gb/s). Some products recently introduced run at data rates of 3.125Gb/s. These SERDES interconnections are commonly implemented usinganalog based technology. All of the modulation/demodulation in theseconventional SERDES is performed in the analog domain. A most commonapproach to modulation is to perform the modulation/demodulation usingbaseband signal processing.

However, these conventional developments fail to provide designs thatoperate at rates sufficiently high for many customer needs and desires.As the data rates increase, the impairments of the transmission mediumbecome more and more important. For example, in the case of amicro-strip transmission line in a printed circuit (PC) board,dispersion (caused by the bandwidth limitations of the transmissionline) causes inter-symbol interference (ISI); discontinuities in thetransmission line cause reflections which also result in ISI; capacitivecoupling between neighboring traces on the PC board causes crosstalk,and other deficiencies as well. Advanced signal processing techniquessuch as equalization and crosstalk cancellation have been applied forseveral decades to control similar impairments in communications systemssuch as voice-band modems, transceivers for the digital subscriber loop,Ethernet transceivers, and so on. However, with the only exception ofthe most straightforward situations, these techniques are too complex tobe implemented using analog circuit design.

In addition, the analog implementation of SERDES may not be easilyscaled to integrated circuit (IC) manufacturing technology of smallerdimensions. For example, a recent trend in Complementary Metal OxideSemiconductor (CMOS) technology has been from a minimum feature size of0.18 μm to 0.13 μm. Design engineers find the analog implementation ofanalog based SERDES extremely difficult. As the processing dimensionscontinue to decrease this situation will only get worse. The inherentnon-scalability of analog based SERDES is a major limitation of theexisting SERDES art.

The inability of analog based SERDES technology to enable advancedmodulation, error correction and signal processing creates a situationwhere the fundamental limits of data rate that may be supported inbackplane interconnections and other SERDES applications may never fullybe realized. An analog based SERDES simply does not offer enoughcapabilities to enable such high data transfer rates.

Further limitations and disadvantages of conventional and traditionalsystems will become apparent to one of skill in the art throughcomparison of such systems with the invention as set forth in theremainder of the present application with reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods of operationthat are further described in the following Brief Description of theSeveral Views of the Drawings, the Detailed Description of theInvention, and the claims. Other features and advantages of the presentinvention will become apparent from the following detailed descriptionof the invention made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a system diagram illustrating various embodiments of DSP basedSERDES that is built according to the present invention.

FIG. 2 is a system diagram illustrating an embodiment of a DSP basedSERDES system that is built according to the present invention.

FIG. 3 is a system diagram illustrating an embodiment of a DSP basedde-serializer interfacing that is built according to the presentinvention.

FIG. 4 is a system diagram illustrating an embodiment of a DSP basedde-serializer that is built according to the present invention.

FIG. 5A is a system diagram illustrating another embodiment of a DSPbased de-serializer that is built according to the present invention.

FIG. 5B is a system diagram illustrating another embodiment of a DSPbased de-serializer that is built according to the present invention.

FIG. 6 is a system diagram illustrating another embodiment of a DSPbased de-serializer that is built according to the present invention.

FIG. 7 is a system diagram illustrating another embodiment of a DSPbased de-serializer that is built according to the present invention.

FIG. 8 is a system diagram illustrating another embodiment of a DSPbased de-serializer that is built according to the present invention.

FIG. 9 is a functional block diagram illustrating an embodiment ofcompensation determination operation that may be performed in accordancewith the present invention.

FIG. 10 is a functional block diagram illustrating an embodiment ofcompensation control operation that may be performed in accordance withthe present invention.

FIG. 11 is a system diagram illustrating an embodiment of a DSP basedparallel decision feedback equalizer (DFE) de-serializer that is builtaccording to the present invention.

FIG. 12 is a system diagram illustrating an embodiment of a parallelimplementation of a DFE that is built according to the presentinvention.

FIG. 13 is a system diagram illustrating an embodiment of a 2-parallelimplementation of a 1-tap DFE that is built according to the presentinvention.

FIG. 14 is a system diagram illustrating an embodiment of a DSP basedde-serializer/receiver that is built according to the present invention.

FIG. 15 is a system diagram illustrating another embodiment of a DSPbased SERDES 1500 that is built according to the present invention.

FIG. 16 is a system diagram illustrating another embodiment of a DSPbased SERDES that is built according to the present invention.

FIG. 17 is a system diagram illustrating a 1-slice embodiment ofautomatic gain control (AGC) that is implemented according to thepresent invention.

FIG. 18 is a system diagram illustrating a 1-slice embodiment of timingrecovery that is implemented according to the present invention.

FIG. 19 is a system diagram illustrating an embodiment of a scramblerthat is employed according to the present invention.

FIG. 20 is a system diagram illustrating an embodiment of a de-scramblerthat is employed according to the present invention.

FIG. 21 is a functional block diagram illustrating an embodiment of aDSP based SERDES de-serializer method that is performed according to thepresent invention.

FIG. 22 is a functional block diagram illustrating another embodiment ofa DSP based SERDES de-serializer method that is performed according tothe present invention.

FIG. 23 is a functional block diagram illustrating another embodiment ofa DSP based SERDES de-serializer method that is performed according tothe present invention.

FIG. 24 is a functional block diagram illustrating another embodiment ofa DSP based SERDES de-serializer method that is performed according tothe present invention.

FIG. 25 is a functional block diagram illustrating an embodiment of aDSP based SERDES training/operating method that is performed accordingto the present invention.

FIG. 26 is a diagram illustrating functionality that may be supported inany of the various embodiments of a DSP based SERDES that is builtaccording to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Great effort has been made in the arena of parallel processingimplementations of DSP. The present invention particularly employsadaptive DSP compensation techniques to enable very high-speed SERDESoperation.

FIG. 1 is a system diagram illustrating an embodiment of DSP basedSERDES interfacing 100 that is built according to the present invention.The DSP based SERDES interfacing 100 is operable to perform chip to chipinterfacing on a single board, chip to chip interfacing between multipleboards, and also board to board interfacing in various embodiments. Inone instance, a board 100 and a board 150 communicatively couple via aDSP based SERDES interconnection 195 that is employed according to thepresent invention. This DSP based SERDES interconnection 195 may verywell be implemented through a back plane 190 to which each of the boards110 and 150 are connected. Each of the boards 110 and 150 has a SERDESinterface circuitry 111 and 151, respectively. The SERDES interfacecircuitries 111 and 151 on the boards 110 and 150 are operable tointerconnect to any other devices on the boards 111 and 151, includingvarious ICs on the boards. Moreover, the applicability of the DSP basedSERDES interfacing 100 may equally be performed in connecting twistedpair cabling, coaxial cabling, and/or twin-ax cable without departingfrom the scope and spirit of the invention. The present invention isgenerically envisioned within any communication interface between atleast two elements.

Alternatively, a DSP based SERDES interconnection 199, that may also beimplemented through the back plane 190, may communicatively couple twodifferent ICs 120 and 160 on the boards 110 and 150. Each of the ICs 120and 160 are operable to interface to the DSP based SERDESinterconnection 199 using SERDES interface circuitry 121 and 161,respectively. The SERDES interfacing circuitry 121 is placed veryclosely to the IC 120, and the SERDES interfacing circuitry 161 isresident as part of the IC 160.

Moreover, a DSP based SERDES interconnection 193 may be used tointerface directly between two ICs, such as the ICs 120 and 160. In thissituation, the ICs 120 and 160 themselves include the proper interfacingfunctionality. This is often the case is many IC application, where theinterfacing is embedded in the IC, requiring only an interconnection andthe DSP based functionality is provided within the IC having thereceiver to receive data via the DSP based SERDES interconnection 193.

Moreover, the present invention is operable to provide forinterconnection between multiple various ICs on a single board as well.For example, the IC 120 is operable to communicatively couple to an IC130 via a DSP based SERDES interconnection 191 on the board 110. In thisexample, a SERDES interface circuitry 131 is resident on the IC 130; theDSP based SERDES interconnection 191 communicatively couples to theSERDES interface circuitry 131 (that communicatively couples to the IC130) and the SERDES interface circuitry 121 (that communicativelycouples to the IC 120).

Those having skill in the art will recognize that the DSP based SERDESinterconnections, built in accordance with the present invention, areoperable to perform high-speed interfacing between a whole host ofdevices, boards, and circuitries.

FIG. 2 is a system diagram illustrating an embodiment of a DSP basedSERDES system 200 that is built according to the present invention. TheDSP based SERDES system 200 is operable to perform communication betweena transceiver 201 and a transceiver 202; each of the transceivers 201and 202 includes a transmitter and a receiver. More specifically, theDSP based SERDES system 200 is operable to perform communication betweena transmitter 230 and a receiver 240 via a serial communication link205. The transmitter 230 is operable to receive data in 210, and ifnecessary, to perform a parallel to serial conversion (as shown in afunctional block 238) of the data in 210 using a serializer 236. Thereceiver 240 is operable to receive the serialized data and to performde-serialization using the de-serializer 246. The de-serializer 246 isoperable to perform serial to parallel conversion, as shown in afunctional block 248. The receiver 240 employs an ADC 242 and a DSP 244to perform the de-serialization of the data to generate data out 250.The ADC 242 and the DSP 244 operate cooperatively. In certainembodiments, several ADCs perform the analog to digital conversion ofthe data received via the serial communication link 205. In addition,multiple DSPs may be employed to perform DSP functionality and relatedmathematical processing on the digital data without departing from thescope and spirit of the invention.

The DSP 244 is able to perform adaptive compensation fornon-uniformities among various interleaves of the ADC 242 (that mayinclude an ADC array), or possible non-uniformities among various otherelements within an analog front-end (AFE) of the receiver 240. As aninput signal enters into the various interleaves of the presentinvention, various offsets mismatches of the different interleaved pathsmay need compensation. The use of DSP 244 to perform compensation forthese various offsets, that may be generated by the non-uniformities ofthe various interleaves, to enable an extremely fast operating DSP basedSERDES. The DSP compensation techniques allow for adaptive compensationof these interleave generated offset mismatches. The ADC 242 and an AFEmay have such impairments, in the case of an interleaved array, that maycooperatively generate fixed pattern noise. While this fixed patternnoise will not be existent within the input signal to the DSP basedSERDES, the interleaved implementation that makes possible the use ofsuch higher speed operation SERDES, may undesirably create this fixedpattern noise. However, the use of DSP correction techniques is operableto overcome these effects. The DSP compensation techniques are able tocompensate for gain, sampling phase and offset errors in the interleavedarray that may lead to the fixed pattern noise.

Again, the DSP 244 is implemented to perform compensation according tothe present invention in an adaptive embodiment. There need be no priorknowledge of the specific values of impairments to the interleaves(being ADCs, other portions of the AFE, and/or channel impairments). TheDSP techniques are able to identify the appropriate compensation and toperform that compensation adaptively. The adaptive DSP compensationimplementation is applicable for both channel impairments andimpairments of the ADCs and/or other portions of the AFE.

Analogously, the DSP based SERDES system 200 is operable to performcommunication between a transmitter 231 and a receiver 241 via a serialcommunication link 207. The transmitter 231 is operable to receive datain 211, and if necessary, to perform a parallel to serial conversion ofthe data in 211. The receiver 241 is operable to receive the serializeddata and to perform de-serialization. The receiver 241 generates dataout 251. The reverse path (from right to left including the transmitter231 and the receiver 241), as shown in the FIG. 2, is also operable toperform all of the associated functionality of the processing shown inthe forward path (from left to right including the transmitter 230 andthe receiver 240) in certain embodiments. Usually, to provide for commonoperations in both receive and transmit paths within a DSP based SERDES,both of the paths are analogous to one another in operation.

FIG. 3 is a system diagram illustrating an embodiment of DSP basedde-serializer interfacing 300 that is built according to the presentinvention. The DSP based de-serializer interfacing 300 is operable toperform interfacing between any two elements, shown as elements 320 and360 in the FIG. 3. It is understood that the elements 320 and 360 mayeach be ICs that may be located on a single board or on different boardswithout departing from the scope and spirit of the invention. Theelements 320 and 360 are operable to communicate via a DSP based SERDESinterconnection 399. The DSP based SERDES interconnection 399 isbi-directional in nature, allowing communication in both directionsbetween the elements 320 and 360.

The element 320 contains a SERDES interface circuitry 321, and theelement 360 contains a SERDES interface circuitry 361. Both SERDESinterface circuitries 321 and 360 are operable to transmit and receivedata via the DSP based SERDES interconnection 399. The SERDES interfacecircuitry 321 includes both transmitter circuitry 322 and receivercircuitry 323. The receiver circuitry 323 includes at least one ADC 324.The ADC 324 could also be multiple ADCs, implemented in an interleavedarray. A signal received by the receiver circuitry 323, and after havingpassed through the ADC 324, is passed to a DSP 327 resident on theelement 320. If desired, a DSP 328 may alternatively be employed withinthe receiver circuitry 323, or a DSP 329 may be implemented on theSERDES interface circuitry 321 itself. The ADC 324 and one, or multiple,of the ADCs 327, 328, and/or 329 operate cooperatively according to thepresent invention to perform high-speed de-serialization of datareceived via the DSP based SERDES interconnection 399.

Similarly, the SERDES interface circuitry 361 includes both transmittercircuitry 362 and receiver circuitry 363. The receiver circuitry 363includes at least one ADC 364. The ADC 364 could also be multiple ADCs,implemented in an interleaved array. A signal received by the receivercircuitry 363, and after having passed through the ADC 364, is passed toa DSP 367 resident on the element 360. If desired, a DSP 368 mayalternatively be employed within the receiver circuitry 363, or a DSP369 may be implemented on the SERDES interface circuitry 361 itself. TheADC 364 and one, or multiple, of the DSPs 367, 368, and/or 369 operatecooperatively according to the present invention to perform high-speedde-serialization of data received via the DSP based SERDESinterconnection 399.

FIG. 4 is a system diagram illustrating an embodiment of a DSP basedde-serializer 400 that is built according to the present invention. TheDSP based de-serializer 400 may be viewed as being in the context of aSERDES 405. Serial data 410 (modulated analog waveform carrying digitaldata) is provided to an ADC 420 within a receiver 420 of the DSP basedde-serializer 400. The output of the ADC 420 (referred to as digitizedserial data, digital serial data, or digital samples of the serial data)is fed to a DSP 440 that extracts the digital data from the serial data410 and outputs parallel data 430 that should fully correspond to thedigital data.

The DSP 440 is operable to perform a variety of various digital signalprocessing operations on the digital samples of the serial data 410(that are output from the ADC 420). Further, the DSP 440 may alsoproduce compensation controls that are provided to other devices thatoperate upon the serial data, either in its analog format or after ithas been digitally sampled. In performing these operations, the DSP 440may utilize any of a number of stored adaptation/compensation options460. These stored adaptation/compensation options 460 may be calculatedoffline and provided to the DSP 440 for subsequent use in compensatingfor non-uniformities in the various interleaves of the DSP basedde-serializer 400. These stored adaptation/compensation options 460 mayinclude compensation of the channel impairments, such as ISI, andcompensation of the impairments of the ADC and possibly other blocks inthe analog front-end, such as gain, sampling phase, or offset mismatchamong the ADCs of an interleaved ADC array. The storedadaptation/compensation options 460 may include one or more pre-computedcompensation operation(s)/compensation control(s) 461, one or morechannel responses 462, signal information 463 (that may include anynumber of types of coding types 464 and modulation schemes 465).

The stored adaptation/compensation options 460 may be calculated andthen stored in a memory 450 that is accessible by the DSP 440. Thememory 450 may be any number of memory types known to those personshaving skill in the art, including random access memory (RAM), read onlymemory (ROM), erasable programmable read only memory (EPROM),electronically erasable programmable read only memory (EEPROM/E2PROM),Ultraviolet electrically programmable read only memory (UVEPROM),re-programmable PROM (RPPROM), and any other memory types as well. Inaddition, the stored adaptation/compensation options 460 mayalternatively be stored on the receiver 420 of the SERDES 405.

However, the DSP 440 is able to perform real time adaptation toadaptively calculate one or more appropriate feedback signals, shown asthe adaptively calculated feedback signal(s) 470. There is typicallyonly one trace through which the serial date 410 (input signal) willpropagates at any time. This is inherent in the serial nature of thecommunication link over which the serial data 410 comes. The DSP isoperable to compensate for mismatches among the interleaves of an ADCarray (that may be viewed as the ADC 420 in the FIG. 4). Therefore, theDSP is able to compensate for impairments due to ADCs, as shown in afunctional block 472. In addition, the DSP 440 is also operable tocompensate for impairments due to gain errors of PGAs, as shown in afunctional block 473, that may be existent in an AFE that first receivesthe serial data 410 and converts it into digital data. The use of PGAsmay be employed here when there is attenuation over the communicationchannel over which the serial data 410 has been transmitted to thereceiver 420.

In addition and generically speaking, the DSP 440 is operable tocompensate for impairment due to the interleaves of any other portionsof the AFE, as shown in a functional block 474. The non-uniformities ofthe various interleaves into which the serial data 410 is placed mayrequire compensation to deal with their inherent variation, that mayresult from imperfections in processing and fabrication of the devices.

Moreover, the DSP 440 is operable to compensate for NEXT and/or FEXT asshown in a functional block 471. The FIG. 4 shows the genericapplicability of the DSP 440 operating to compensate, adaptively in realtime, for a variety of impairments that may result from the inherentinterleaving, channel nature of DSP based de-serializing according tothe present invention. In addition, the stored adaptation/compensationoptions 460 show how the DSP 440 may also use somepre-stored/pre-calculated compensation options in certain situations.

In the context of data communications applications, the DSP 440 isoperable to compare the digital data received from the ADC 420 againstat least the signal information 463. Additionally, the ADC 420 maycompare the digital data received from the ADC 420 against the channelresponses 462, or a combination of the signal information 463 and thechannel responses 462. In one embodiment of making this determination,the DSP 440 first determines the modulation scheme employed by a coupledSERDES transmitter that produced the serial data. Various modulationschemes 465 may be employed including on-off keying (or 2-level pulseamplitude modulation, PAM-2), multilevel PAM (for example, 4-PAM thatencodes 2 bits per symbol and therefore double the data rate achievablefor a given symbol rate), among other modulation schemes known bypersons having skill in the art. In addition, more elaborate modulationschemes, including single carrier quadrature amplitude modulation (QAM:such as 16 QAM, 64 QAM, 256 QAM, and/or 1024 QAM) or multi-carriermodulation are possible, as understood by those persons having skill inthe art. Based upon this determination, the DSP 440 adapts itsoperations to expect a particular modulation scheme, and optionally, aparticular channel response. Such adaptation is performed based uponknown characteristics of the serial data 410 as provided by the signalinformation 463 and optionally the channel information.

The DSP 440 is also operable to discern the data coding type of theserial data 410. Similarly, the present invention is operable to adaptto a variety of input coding types 464 known by those persons havingskill in the art. For example, the present invention may be used incombination with techniques such as Viterbi decoding, convolutionalcoding, block coding, trellis coding, and any other form of modulationcoding or error correction coding. In addition, turbo coding may beemployed as well as various types of pre-coding without departing fromthe scope and spirit of the invention, including Tomlinson-Harashimapre-coding and Dynamics Limited Pre-coding.

With the DSP 440 adapted to a particular modulation type (and optionallycoding type and channel response), the DSP 440 has foreknowledge that itmay use to compare the digitized serial data against correct signalinformation (the signal information 463) stored in the storedadaptation/compensation options 460 (during a training sequence orduring normal operations). Based upon this comparison, the DSP 440determines necessary compensation operations that it will perform on thedigitized serial data and/or compensation control operations that ituses to control other components that perform compensation operations onthe serial data. With these compensation operations performed, thereceiver may then accurately extract digital information from the serialdata 410.

If desired, and as will be shown in various embodiments, theadaptation/compensation performed by the DSP 440 may be performed usingparallel processing techniques on a number of channels into which thenow digital form of the serial data 410 has been channeled. The DSP 440may then determine the proper compensation controls required, if any,from the one or more pre-computed compensation controls 461 that arestored in the stored adaptation/compensation options 460 and to applysuch feedback signal(s) in compensation control operations.

FIG. 5A is a system diagram illustrating another embodiment of a DSPbased de-serializer 500A that is built according to the presentinvention. Serial data 500A is fed to an ADC 540A. The output of the ADC540A is digital data having a word width of n. The now digital data isfed to a DSP 550A. The DSP 550A is operable to perform compensationdetermination 551A and to identify any compensation operations 552A thatneed to be performed concerning the serial data 510A, in light of theanalog to digital conversion that it undergoes in the ADC 540A.Compensation control 520A is fed back to the ADC 540A as required toaccommodate the now digital form of the serial data 510A. The ADC 540Ais adjusted, as required to ensure a properly sampled digital signal.Fixed pattern noise is typically repetitive based on the degree ofmismatch in system parameters including gain mismatch, phase mismatch,offset mismatch, and other mismatches. By adjusting the ADC 540A, fixedpattern noise is significantly reduced or eliminated. If desired, one orall of these various parameters are dealt with by adjusting the digitalsampling of the serial data 510A.

Again, the DSP 550A is operable not only to determine which necessarycompensation is desirable to achieve a properly sampled signal(compensation determination 551A), but the DSP 550A is also operable todetermine those compensation operations 552A, when provided to the ADC540A, would effectuate a properly sampled signal. These compensationoperations 552A are passed to the ADC 540A via a feedback signal shownas compensation control 520A. As described in other of the variousembodiments, the particular context of data communications applications,where a vast amount of information is discernible concerning the serialdata 510A, and the communication channel over which the serial data 510Ahas come, one or both of the compensation determination 551A and thecompensation operations 552A may be identified using a predeterminednumber of stored feedback compensation options. This foreknowledge ofthe incoming serial data 510A allows very effective compensation to curbthe effects of fixed pattern noise in the context of data communicationsapplications and other applications where fixed pattern noise arises.The digital correction techniques are very well adapted to performingcompensation to the fixed pattern noise problem, again, based on thisknowledge of the incoming signal to the ADC 540A and also based on theknowledge of the type of channel over which the incoming signal hascome.

From some perspectives, the DSP 550A is able to perform adaptivecompensation for non-uniformities among various interleaves of the ADC540A (that may include an ADC array), or possible non-uniformities amongvarious other elements within an analog front-end (AFE) of the DSP basede-serializer 500A. As an input signal enters into the variousinterleaves of the present invention, various offsets mismatches of thedifferent interleaved paths may need compensation. The use of DSP 550Ato perform compensation for these various offsets, that may be generatedby the non-uniformities of the various interleaves, to enable anextremely fast operating DSP based de-serializer 500A. The DSPcompensation techniques allow for adaptive compensation of theseinterleave generated offset mismatches. The ADC 540A and an AFE may havesuch impairments, in the case of an interleaved array, that maycooperatively generate fixed pattern noise. While this fixed patternnoise will not be existent within the input signal to the DSP basedde-serializer 500A, the interleaved implementation may undesirablycreate this fixed pattern noise. However, the use of DSP correctiontechniques is operable to overcome these effects. The DSP compensationtechniques are able to compensate for gain, sampling phase and offseterrors in the interleaved array that may lead to the fixed patternnoise.

Again, the DSP 550A is implemented to perform compensation according tothe present invention in an adaptive embodiment. There need be no priorknowledge of the specific values of impairments to the interleaves(being ADCs, other portions of the AFE, and/or channel impairments). TheDSP techniques are able to identify the appropriate compensation and toperform that compensation adaptively. The adaptive DSP compensationimplementation is applicable for both channel impairments andimpairments of the ADCs and/or other portions of the AFE.

Moreover, it is also noted that the adaptive DSP compensationimplementation may be performed for NEXT and FEXT crosstalk problemswithin a communication channel that provides the serial data 510A to theADC 540A. The embodiment of the FIG. 5A specifically shows theembodiment where this adaptive compensation is performed via thecompensation control 520A that is provided from the DSP 550A to the ADC540A. The following FIG. 5B will show how this adaptive compensation maybe performed within a DSP itself.

FIG. 5B is a system diagram illustrating another embodiment of a DSPbased de-serializer 500B that is built according to the presentinvention. Serial data 500B is fed to an ADC 540B. The output of the ADC540B is parallel digital data having a word width of n. The now digitaldata is fed to a DSP 550B. The DSP 550B is operable to performcompensation determination 551B and to identify any compensationoperations 552B that needs to be performed concerning the serial data510B, in light of the analog to digital conversion that it undergoes inthe ADC 540B. Compensation control 520B is fed external to DSP 550B, asshown in the embodiment of the FIG. 5B, as required to accommodate thenow digital form of the serial data 510B. The DSP 550B performedmathematical processing on the now digital form of the serial data 510B,as required to ensure that the now digital data is in a form that wouldbe achieved were the operation of the ADC 540B substantially ideal. Thisdigital signal processing of the now digital form of the serial data510B, as performed by the DSP 50B, ensures that there is a properlysampled digital signal. The concerns of fixed pattern noise, that istypically repetitive based on the degree of mismatch in systemparameters including gain mismatch, phase mismatch, offset mismatch, andother mismatches, are minimized performing digital signal processing toeffectuate what appears to be an adjustment of the ADC 540B; the digitaloutput signal from the ADC 540B is mathematically modified to generate adigital signal that has all the proper characteristics of a properlysampled signal, as if the ADC 540B performed a proper sampling of theserial data 510B. If desired, one or all of these various parameters aredealt with by performing digital signal processing on the digital datausing the DSP 550B.

In this embodiment, the DSP 550B is operable not only to determine whichnecessary compensation is desirable to achieve a properly sampled signal(compensation determination 551B), but the DSP 550B is also operable todetermine those compensation operations 552B, and to actually performthe compensation control 553B itself as to effectuate a digital signalhaving the characteristics of a properly sampled signal. As described inother of the various embodiments, the particular context of datacommunications applications, where a vast amount of information isdiscernible concerning the serial data 510B, and the communicationchannel over which the serial data 510B has come, one or both of thecompensation determination 551B and the compensation operations 552B maybe identified using a predetermined number of stored feedbackcompensation options. This foreknowledge of the incoming serial data510B allows very effective compensation to curb the effects of fixedpattern noise in the context of data communications applications andother applications where fixed pattern noise arises. The digitalcorrection techniques are very well adapted to performing compensationto the fixed pattern noise problem, again, based on this knowledge ofthe incoming signal to the ADC 540B and also based on the knowledge ofthe type of channel over which the incoming signal has come.

From some perspectives, the DSP 550B is able to perform adaptivecompensation for non-uniformities among various interleaves of the ADC540B (that may include an ADC array), or possible non-uniformities amongvarious other elements within an analog front-end (AFE) of the DSP basede-serializer 500B. As an input signal enters into the variousinterleaves of the present invention, various offsets mismatches of thedifferent interleaved paths may need compensation. The use of DSP 550Bto perform compensation for these various offsets, that may be generatedby the non-uniformities of the various interleaves, to enable anextremely fast operating DSP based de-serializer 500B. The DSPcompensation techniques allow for adaptive compensation of theseinterleave generated offset mismatches. The ADC 540B and an AFE may havesuch impairments, in the case of an interleaved array, that maycooperatively generate fixed pattern noise. While this fixed patternnoise will not be existent within the input signal to the DSP basedde-serializer 500B, the interleaved implementation may undesirablycreate this fixed pattern noise. However, the use of DSP correctiontechniques is operable to overcome these effects. The DSP compensationtechniques are able to compensate for gain, sampling phase and offseterrors in the interleaved array that may lead to the fixed patternnoise.

Again, the DSP 550B is implemented to perform compensation according tothe present invention in an adaptive embodiment. There need be no priorknowledge of the specific values of impairments to the interleaves(being ADCs, other portions of the AFE, and/or channel impairments). TheDSP techniques are able to identify the appropriate compensation and toperform that compensation adaptively. The adaptive DSP compensationimplementation is applicable for both channel impairments andimpairments of the ADCs and/or other portions of the AFE.

Moreover, it is also noted that the adaptive DSP compensationimplementation may be performed for NEXT and FEXT crosstalk problemswithin a communication channel that provides the serial data 510B to theADC 540B. The embodiment of the FIG. 5B specifically shows theembodiment where this adaptive compensation is performed within the DSP550B itself.

FIG. 6 is a system diagram illustrating another embodiment of a DSPbased de-serializer 600 that is built according to the presentinvention. Serial data 610 is provided to compensation circuitry 652.The compensation circuitry 652 is operable to perform modification ofthe serial data 610 before an analog to digital conversion using an ADC640. The compensation circuitry 652 is operable to perform varioustransfer function operations on the serial data 610, using analog basedcircuitry components, to pre-compensate for the impairments of the ADC640. The output of the ADC 640 is parallel digital data having a wordwidth of n. The now digital data is fed to a DSP 650. The DSP 650 isoperable to identify what compensation determination 651 is required andalso to identify compensation operations 654 in various embodiments.

From the DSP 650, compensation control 620 is fed back to one or both ofthe ADC 640 and the compensation circuitry 652. If desired, thecompensation circuitry 652 is operable to receive information concerningthe compensation determination 651 that is determined by the DSP 650,and then the compensation circuitry 652 may also have intelligence sothat it may itself identify compensation operations 653 that should beperformed to compensate for deficiencies in the ADC 640. In addition, itis also noted that the ADC 640 is also operable to be adjusted, insimilar manner to other ADCs as described in various other embodimentsof the present invention to deal with ADC-related non-uniformities. Anygain, phase, offset or other deleterious effects introduced by theanalog to digital conversion within the ADC 640 may be addressed byproper adjustment of the ADC 640, as governed by the feedback signalshown as compensation control 620.

It is also noted that in this embodiment, as well as in otherembodiments, the DSP block (shown as DSP 650 in the FIG. 6) may includea single DSP or multiple DSPs as well without departing from the scopeand spirit of the invention. Those persons having skill in the art willappreciate that a number of co-DSPs may also be employed, or a number ofmathematical logic processing circuitries, may also be employed toperform the digital signal processing of the now digital data toeffectuate a digital signal having the characteristics of a properlysampled signal.

From certain perspectives, this embodiment shows the ability of thepresent invention to perform accommodation of fixed pattern noiserelated problems by dealing with these problems before any analog todigital conversion of the analog signal. Other embodiments have shownthat the present invention is operable to deal with the fixed patternnoise problem by adjusting the operational parameters of the ADC itself,by performing mathematical processing of the digital data coming out ofan ADC, and this embodiment shows the ability to deal with the fixedpattern noise problem by performing compensation of the analog signalusing a compensation circuitry 652 that is situated before the ADC 640.In addition, this embodiment shows the ability to perform hybridcompensation as well, by performing some compensation in thecompensation circuitry 652, and some compensation by adjusting theoperational parameters of the ADC 640. Similarly, the present inventionis also operable to perform hybrid compensation in other embodiments aswell. For example, the present invention allows implementation ofcombinations of compensation to be performed in various sections of asystem that is built according to the present invention. Compensationmay be performed before the analog to digital conversion, within the ADCperforming the analog to digital conversion, and also in a DSP situatedafter the ADC as well. The deleterious effects of fixed pattern noiseand other recurring noise problems are aptly dealt with using thesecompensation aspects of the present invention.

FIG. 7 is a system diagram illustrating another embodiment of a DSPbased de-serializer 700 that is built according to the presentinvention. A serial data signal 710 is fed to an ADC array 720 thatitself has a number of ADCs, shown as an ADC #1 721, an ADC #2 722, . .. , and an ADC #n 729. The serial data 710 is fed simultaneously to eachADC within the ADC array 720. Each ADC within the ADC array 720 isoperable to sample at a sampling rate lower than the total or effectivesampling rate. The sampling of the ADCs within the ADC array 720 isperformed so as to effectuate a higher sampling rate of any of the ADCswithin the array. The effective sampling rate of the ADC array 720 maybe viewed as being the total sampling rate of each of the sampling ratesof the ADCs within the ADC array 720 when summed together. For example,in an embodiment where n=8, then an effective sampling rate of 10 GHzcan be achieved with 8 interleaved ADCs each running at 1.25 GHz. Eachof the ADCs within the ADC array 720 performs sampling at differenttimes within a given cycle of the serial data 710.

In addition, each of the ADCs within the ADC array 720 may individuallybe controlled to effectuate a proper sampling of the serial data 710.For example, the gain, phase, offset, and other operational parametersof each of the ADCs within the ADC array 720 may be adjusted to ensurethat the sampling of the various ADCs is performed uniformly and withproper phase and time delays between the samples, thereby ensuring thatthe digital data is a true rendition of the serial data 710. Each of theADCs within the ADC array 720 may be viewed as generating a channel,properly spaced in time from the other channels, that is generated bythe other ADCs within the ADC array 720. Each of these channels is fedto a DSP 750.

Again, it is also noted that in this embodiment, as well as in otherembodiments, the DSP block (shown as DSP 750 in the FIG. 7) may includea single DSP or multiple DSPs as well without departing from the scopeand spirit of the invention. Those persons having skill in the art willappreciate that a number of co-DSPs may also be employed, or a number ofmathematical logic processing circuitries, may also be employed toperform the digital signal processing of the now digital data toeffectuate a digital signal having the characteristics of a properlysampled signal.

The DSP 750 is operable to determine any parallel based compensationthat may be required to transform the now digital, parallel form of theserial data 710, so as to generate digital data having the propercharacteristics including proper gain, phase, offset, and othercharacteristics (as shown in the functional block 751). The parallelbased compensation determination 751 creates compensation controlsindividually for each of the ADCs within the ADC array 750. That is tosay, a parallel based feedback signal, shown as compensation control715, may be fed back to the ADC array 720, such that differentcomponents of a digital word may be used to adjust the operationalcharacteristics of the individual ADCs of the ADC array 720. The use ofa digital word, having various bits or bit segments within the digitalword, to adjust different ADCs within the ADC array 720 will beunderstood by those persons having skill in the art. In addition, ifdesired, the DSP 750 is operable not only to perform the parallel basedcompensation determination 751, but also to identify precisely thoseparallel based compensation operations 752 that will effectuate thedesired operation of the ADC array 750.

Moreover, in even other embodiments, the DSP 750 is operable to identifyand also operable to perform parallel based compensation control 753within the DSP 750 itself. The DSP 750 is operable to perform thecompensation control 753 alone, without feeding back and compensationcontrol 715, yet it is also operable to perform compensation incooperation with the ADC array 720 to which compensation control 715 ispassed. Such an embodiment shows the ability of the present invention toperform hybrid type of compensation for the many deleterious effectspresent in the prior art that have, until now, prevented an effectiveimplementation of a DSP-based de-serializer.

It is also noted that the parallel based compensation determination 751,the parallel based compensation operations 752, and the parallel basedcompensation control 753 may all be performed independently for variousinterleaves within the DSP based de-serializer 700. That is to say, thevarious interleaves may undergo independent determination,identification of operations, and control according to the presentinvention.

FIG. 7 shows a parallel implementation of a number of interleaved ADCs,in the ADC array 720, that enable a much higher sampling rate that theindividual sampling rate of the individual ADCs within the ADC array720. Those persons having skill in the art will also appreciate that anynumber of ADC arrays may be interleaved without departing from the scopeand spirit of the invention. In a similar manner in which the individualADCs within the ADC array 720 are interleaved, a number of ADC arraysmay themselves be interleaved thereby providing a much higher effectivesampling rate of the serial data 710; ADC arrays could be interleaved,with each ADC having a number of ADCs, to effectuate higher samplingrates as well.

FIG. 8 is a system diagram illustrating another embodiment of a DSPbased de-serializer 800 that is built according to the presentinvention. A serial data 810 is provided to compensation circuitry 852.This is an analog signal representing the serial data stream transmittedfrom the serializer after traversing the communication channel. It maybe modulated using any modulation scheme, such as pulse amplitudemodulation (PAM), quadrature amplitude modulation (QAM), multi-carriermodulation, etc. The compensation circuitry 852 is operable to performmodification of the signal 810 before an analog to digital conversion.The compensation circuitry 852 is operable to perform various transferfunction operations on the signal 810, using analog based circuitrycomponents, pre-compensate for the impairments of the ADC and otherblocks of the analog front end. Within an actual system, variousimperfections, including device imperfections may contribute to a signalhaving fixed pattern noise problems. The compensation circuitry 852 isoperable to curb these effects so that the analog to digital conversion(digital sampling of the serial data 810) generates digital data that istruly representative of the serial data 810. After passing through thecompensation circuitry 852, the now pre-compensated (if necessary)serial data 810 is presented to the ADC array 820. The output of the ADCarray 820 is parallel digital data having a word width of n. The nowdigital data is fed to a DSP 850. In various embodiments, the DSP 850 isoperable to identify what compensation would achieve what would be aproperly sampled signal and also to identify compensation operations, asshown by combined functional block compensation/operations 851.

It is also noted that the combined functional blockcompensation/operations 851 may be performed independently for variousinterleaves within the DSP base de-serializer 800. That is to say, thevarious interleaves may undergo independent determination,identification of operations, and control according to the presentinvention.

From the DSP 850, compensation control 820 is fed back to one or both ofthe ADC array 820 and the compensation circuitry 852. The compensationcontrol, when fed to the ADC array 820, is operable to performadaptation of the entire ADC array 820, or alternatively, to each of theindividual ADCs within the ADC array 820. If desired, the compensationcircuitry 852 is operable to receive information concerning thecompensation determination that is determined by the DSP 850, and thenthe compensation circuitry 852 may also have intelligence so that it mayitself identify compensation operations 854 that should be performed tocompensation for deficiencies in the incoming serial data 810. Thecompensation circuitry 852, when operable to identify the compensationoperations 854, is able to identify the compensation operations 854independently or in conjunction with the DSP 850. In addition, it isalso noted that the ADC array 820 is also operable to be adjusted, insimilar manner to other ADCs as described in various other embodimentsof the present invention to deal with ADC-related non-uniformities. Anygain, phase, offset or other deleterious effects introduced by theanalog to digital conversion performed within the ADC array 840 (or anyof the individual ADCs within the ADC array 840), may be addressed byproper adjustment of the ADC 840, as governed by the feedback signalshown as compensation control 820.

It is also noted that in this embodiment, as well as in otherembodiments, the DSP block (shown as DSP 850 in the FIG. 8) may includea single DSP or multiple DSPs as well without departing from the scopeand spirit of the invention. Those persons having skill in the art willappreciate that a number of co-DSPs may also be employed, or a number ofmathematical logic processing circuitries, may also be employed toperform the digital signal processing of the now digital data toeffectuate a digital signal having the characteristics of a properlysampled signal.

FIG. 8 shows a parallel implementation of a number of interleaved ADCs,in the ADC array 820, that enable a much higher sampling rate that theindividual sampling rate of the individual ADCs within the ADC array820. Those persons having skill in the art will also appreciate that anynumber of ADC arrays may also be interleaved without departing from thescope and spirit of the invention. In a similar manner in which the ADCswithin the ADC array are interleaved, thereby providing a much highereffective sampling rate of the serial data 810, a number of ADC arrayscould also be interleaved, with each ADC having a number of ADCs, toeffectuate higher sampling rates as well.

FIG. 9 is a functional block diagram illustrating an embodiment ofcompensation determination operation 900 that may be performed inaccordance with the present invention. In FIG. 9, the variousembodiments of the present invention are shown to be operable to performcompensation determination 910. In the compensation determination 910functional block, the present invention is operable to perform analysisof an ADC output signal using a DSP, as shown as a functional block 920.In performing the analysis of an ADC output signal using a DSP, thepresent invention is operable to perform comparison to any number ofstored options 9210, including one or more pre-computed feedback signals961, one or more channel responses 962, one or more signal types 963,one or more coding types 964, . . . , and one or more other options 969.

As also described in other of the various embodiments of the presentinvention, the present invention is operable to ascertain variouscharacteristics of an incoming analog signal, once it has been sampledand transformed into the digital realm. A DSP is operable to performanalysis of the digital signal against a number of stored parameters. Inthe context of data communications applications, a large degree ofknowledge may be discerned concerning the channel response of acommunication link over which an analog data signal has come beforearriving at an ADC that performs analog to digital conversion of ananalog signal. Given the context of data communications applications, apredetermined number of pre-computed feedback signal, shown asfunctional block 961, may be calculated based on the finite number offeedback options that would be required to compensate for problems ofgain, phase, offset, and other deleterious effects that may arise fromanalog to digital conversion in an ADC, and also to other deficienciesthat may be introduced within the system before the signal has made itsway to the ADC.

FIG. 10 is a functional block diagram illustrating an embodiment ofcompensation control operation 1000 that may be performed in accordancewith the present invention. The compensation control operation 1000shows the various aspects of compensation control 1010 that may beperformed in various embodiments. Mismatch/error compensation 1020 andparallel based compensation 1030 are two types of compensation control1010 that may be performed in accordance with the present invention. Insimilar manner that the present invention can determine the compensationthat would be suitable to transform a digitally sampled version of ananalog signal into a signal that has proper characteristics of parameterincluding gain, phase, offset, the present invention is also operable toidentify those adaptations and transformations that would ensure thatthe digitally sampled signal will contain the proper characteristics ofa signal having the proper characteristics.

In some situations, when a signal is made up of various signalcomponents that are combined into a single signal, some will arrive atan ADC having some fixed pattern noise related deficiencies. The presentinvention is operable to curb these effects. This particular ability ofthe present invention shows the ability of the present invention tocompensate for deficiencies of fixed pattern noise that may beintroduced in analog to digital conversion within an ADC, and also tocompensate for fixed pattern noise related problems in the overallsystem itself.

In addition, the present invention is operable to perform compensationfor deficiencies and non-uniformities within an ADC array. This isparticularly applicable in the context of systems employing an ADCarray, in which multiple ADCs perform sampling at different times, andthe operation of all of the ADCs within the ADC array may benon-uniform. In addition, the various ADCs may introduce non-uniformdifferences of phase between the various channels serviced by the ADCarray. The present invention is operable to compensate for this byadjusting the phase of the various channels appropriately, as shown in afunctional block 1022. The phase of some channels may be advanced, andthe phase of other channels in an ADC array may be delayed, to ensurethat the channels each sample the incoming signal appropriately, with aproper spacing of time and phase between the various channels. Oneadditional problem that may arise is when the various ADCs eachintroduce a non-uniform amount of offset into the signal during theanalog to digital conversion; the various ADCs may have slightlydifferent characteristics that generate this offset. The presentinvention is also operable to compensate for deficiencies in non-uniformoffset (as shown in the functional block 1025), as well as eliminate anyamount of offset at all, that may be introduced as an offset into thenow-digital data that represents the incoming analog signal that isprovided to an ADC. In addition, the present invention is operable toperform compensation of crosstalk in the form of NEXT 1021 and/or FEXT1024. The present invention is also operable to perform compensation ofADC gain mismatch 1023, as well as to accommodate any problems ordeficiencies of channel response 1027 as well. Some problems may arisewhen the incoming signal, or at least portions of the incoming signal,arrives at the ADC across different signal paths. However, more commonthat that will be problems arising due to non-uniformities between thevarious ADCs within an ADC array that is employed according to thepresent invention.

The ADC gain mismatch 1023 may be generated in all, or in part, by theanalog to digital conversion operation. The ADC gain mismatch 1023 mayalternatively be generated in all, or in part, by the other parts of thesystem before the analog to digital conversion in an ADC. Similarly, thetiming mismatch 1026 may be generated in all, or in part, by the analogto digital conversion operation. The present invention is operable tocompensate for these deleterious effects using DSP-based compensationtechniques, by performing mathematical processing of the digital data inthe DSP domain, or alternatively, to perform analog-based signalprocessing by modifying certain analog circuitries before the ADC, asidentified and determined, at least in part, by a DSP that is placedafter the ADC (which may be an ADC array) that performs the analog todigital conversion. The DSP is the entity that is operable, at least, toidentify the compensation (if any) to be performed. In certainembodiments, the DSP performs the compensation in the digital domain,performing mathematical processing on the digital data.

Again, the compensation of the present invention may be performed usingparallel based compensation 1030 by performing arraycompensation/adjustment 1040 that is operable to be implemented on anindividual device basis 1042. Alternatively, the arraycompensation/adjustment 1040 may also be performed on an entire arraybasis 1044. The array may very well be an ADC array, as described invarious embodiments, but the array may be an alternative device. Forexample, an array of filters or an array of voltage scaling circuitry(to adjust gain) may be placed before the ADC that performs analog todigital conversion. The array may be selectively switched in andoperated to perform modification of certain channels of an analogsignals that are fed to various ADCs in an ADC array. These devices maybe PGAs that may be adjusted and controlled using AGC. In addition, asdescribed in various embodiments, the parallel based compensation 1030may be performed after an analog to digital conversion 1054 where theparallel based compensation 1030 may be performed using digital signalprocessing 1055. Alternatively, the parallel based compensation 1030 maybe performed before an analog to digital conversion 1052 where theparallel based compensation 1030 may be performed using analog circuitry1053. Again, the direction and control of precisely how to configure theanalog circuitry 1053 may also be determined and controlled usingdigital signal processing.

FIG. 11 is a system diagram illustrating an embodiment of a DSP basedparallel decision feedback equalizer (DFE) de-serializer 1100 that isbuilt according to the present invention. Serial input data 1110 is fedsimultaneously to a number of PGAs, shown as a PGA 1121, a PGA 1122, aPGA 1123, . . . , and a PGA 1129. The outputs of each of the PGAs formchannels for the serial input data 1110, after undergoing any gainadjustment using the PGAs 1121-1129. The output of each of these PGAs isfed to an ADC where the serial data is sampled using a number of ADCs,shown as an ADC 1131, an ADC 1132, an ADC 1133, . . . , and an ADC 1139.Together, the ADCs 1131-1139 operate to achieve an effective samplingrate of the sum total of each of the sampling rates of the ADCs1131-1139. Each of the ADCs 1131-1139 operates at substantially the samesampling rate. Additional intelligence may be employed in variousembodiments to accommodate the situation where some of the ADCs operateat different sampling rates as the other of the ADCs. The outputs ofeach of the ADCs are fed to a precursor filter 1140. The precursorfilter 1140 performs the operation of properly creating zero crossingsin the now digital samples. The precursor filter 1140 also performspulse shaping to ensure that the pulse is in the proper shape so as toenable timing recovery, as will be described below as well as in othervarious embodiments. The pulse is effectively transformed into a shapethat allows effective operation of the timing recovery.

The outputs of the channels, after they have passed through theprecursor filter 1140, are fed to a DFE 1150 that is implemented in aparallel manner. The output from the DFE 1150 is provided as paralleldigitized data 1130. In addition, the parallel digitized data 1130 isalso sampled and provided to two feedback functional blocks, namely, atiming recovery functional block 1160 and an AGC functional block 1170.The timing recovery functional block 1160 is operable to provide clocksignals that are adapted as necessary, to each of the ADCs 1131-1139. Inaddition, the AGC functional block 1170 is operable to provide gaincontrol signals to the PGAs 1121-1129.

The timing recovery functional block 1160 is operable to performadjustment of the sampling times at which the various ADCs 1131-1139 mayhave sampled the incoming serial input data 1110. For example, the ADCs1131-1139 may not operate ideally and may sample the serial input data1110 at non-uniformly spaced times. To compensate and correct for thisdeficiency in a non-ideal array of ADCs, the timing recovery functionalblock 1160 is operable to adjust the time at which the ADCs effectivelysample the serial input data 1110; more precise clock signals may beprovided to the ADCs via the timing recovery functional block 1160. TheAGC functional block 1170 is operable to provide input to the PGAs1121-1129 to ensure that the gain of the serial input data 1110 isappropriate for the particular data type, channel response, andapplication context. The gain of the various channels into which theserial input data 1110 is partitioned, after having passed through thePGAs 1121-1129, may then be appropriately adjusted.

The following FIGS. 12 and 13 illustrate example embodiments of howparallel implementation of a DFE may be performed. These parallelimplementations show just some examples of how a number of parallelpaths may be generated. These parallel DFE architectures show just someof the broad range of parallel based embodiments in which the operationsof the present invention may be performed. These parallel techniques andadditional parallel techniques and details may be found in the followingpublication:

-   Sanjay Kasturia and Jack H. Winters, “Techniques for High-Speed    Implementation of Nonlinear Cancellation,” IEEE Journal on Selected    Areas in Communications, vol. 9, no. 5, June 1991.

FIG. 12 is a system diagram illustrating an embodiment of a parallelimplementation of a decision feedback equalizer (DFE) 1200 that is builtaccording to the present invention. All the possible values of afeedback signal are pre-computed, and the selection of the appropriatefeedback signal is selected using a multiplexor (MUX).

As shown in the 1-tap DFE embodiment of the FIG. 12, an input signaly_(n) is fed simultaneously along two channels, one of which is acomparator 1211 and one of which is a comparator 1212. The comparatorthresholds may be set to any desired values (−h₁ and +h₁) as required ordesired for various applications. The output of the comparator 1211 isfed to a time delay z⁻¹ 1221, from which an output signal shown an A_(n)is provided to a MUX 1230; the output of the comparator 1212 is fed to atime delay z⁻¹ 1222, from which an output signal shown an B_(n) isprovided to the MUX 1230. The output from the MUX 1230, shown as a_(n),is fed to a time delay z⁻¹ 1240, from which an output signal a_(n-1) isultimately output from the serial to parallel implementation of the DFE1200.

The number of pre-computed feedback signals are stored in the MUX 1230,and the appropriate feedback signal is selected, as provided by theoutput signal a_(n-1) that is fed back to select “Sel” from the MUX1230. Rather that need to calculate the feedback signal, the presentinvention is operable to switch in the appropriate feedback signal basedon information it may easily acquire including the input signal type andthe channel response. In contradistinction to other implementations of aDFE, the present invention is operable to move the comparators 1211 and1212 out of the feedback loop. The time delays 1221 and 1222 are addedin to compensate and give time for the slowness of the comparators 1211and 1212. For example, in some embodiments, the operational speed of thecomparators 1211 and 1212 and the operational speed of the MUX 1230 maybe of longer duration than a clock cycle. The present invention benefitsgreatly by the introduction of the time delays 1221 and 1222 tocompensate for this possibility.

From certain perspectives, the FIG. 12 shows a first step ofimplementation of a DFE, where all of the possible feedback signals arepre-computed, and a slicer in the feedback loop is replaced by a MUX.

A second step is to perform the look-ahead transformation in doing theserial to parallel implementation of the DFE. The look-aheadtransformation involves employing the following equations:a _(n) =A _(n) a _(n-1) +Bā _(n-1)a _(n-1) =A _(n-1) a _(n-2) +B _(n-1) ā _(n-2)

Then, the second expression is replaced into the first expression asfollows:a _(n)=(A _(n) A _(n-1) +B _(n) A _(n-1))a _(n-2)+(A _(n) B _(n-1) +B_(n) + B _(n-1))ā _(n-2)

Then, we have the following result:a _(n-1)=(A _(n-1) A _(n-2) +B _(n-1) A _(n-2))a _(n-3)+(A _(n-1) B_(n-2) +B _(n-1) + B _(n-2))ā _(n-3)

The look-ahead transformation is understood in the context of parallelprocessing by those persons having skill in the art. By getting a interms of a_(n-2), the clock speed may effectively be slowed by a factorof 2. If desired, the look-ahead transformation may also be performedmultiple times, getting a in terms of a_(n-m), the clock speed mayeffectively be slowed by a factor of m. Those persons having skill inthe art will understand the extendibility of such operations toeffectively allow operation at slower clock frequencies while stillmaintaining performance.

FIG. 13 is a system diagram illustrating an embodiment of a 2-parallelimplementation of a 1-tap decision feedback equalizer (DFE) 1300 that isbuilt according to the present invention. From certain perspectives,FIG. 13 may be viewed as being a hardware implementation of thelook-ahead transformation equations described above. The DFE is oneexample of an embodiment of how the present invention may beparallelized. Some equalization and compensation methods may not easilybe parallelized, but the present invention is adaptable to take fulladvantage of any of those equalization and compensation methods that maybe parallelized.

Here, the present invention shows its adaptability to operate with aclock signal that is reduced by a factor of 2. Two parallel paths of theDFE are used in the FIG. 13. As shown in the 1-tap DFE embodiment of theFIG. 13, an input signal y_(n) is fed simultaneously along two channels,one of which is a comparator 1311 and one of which is a comparator 1312.The comparator thresholds may be set to any desired values (−h₁ and +h₁)as required or desired for various applications. The output of thecomparator 1311 is fed to a time delay z⁻² 1321, from which an outputsignal shown an A_(n) is provided to combinatorial logic 1330; theoutput of the comparator 1312 is fed to a time delay z⁻² 1322, fromwhich an output signal shown an B_(n) is provided to the combinatoriallogic 1330. The output from the combinatorial logic 1330, shown asa_(n), is fed to a time delay z⁻² 1340, from which an output signala_(n-2) is ultimately output as the first output from the 2-parallelimplementation of a 1-tap DFE 1300.

Analogously, an input signal y_(n-1) is fed simultaneously along twochannels, one of which is a comparator 1351 and one of which is acomparator 1352. The comparator thresholds may be set to any desiredvalues (−h₁ and +h₁) as required or desired for various applications.The output of the comparator 1351 is fed to a time delay z⁻² 1361, fromwhich an output signal shown an A_(n-1) is provided to combinatoriallogic 1370; the output of the comparator 1352 is fed to a time delay z⁻²1362, from which an output signal shown as B_(n-1) is provided to thecombinatorial logic 1370. The output from the combinatorial logic 1370,shown as a_(n-1), is fed to a time delay z⁻² 1380, from which an outputsignal a_(n-3) is ultimately output as the second output from the2-parallel implementation of a 1-tap DFE 1300.

The operations of the combinatorial logics 1330 and 1370 are operable toperform the combination of the two parallel paths in this embodiment. Asthe number of parallel paths increases, as may be performed inalternative embodiments, the complexity of the combinatorial logicsassociated will also be increased. However, the increase in complexityof the combinatorial logic is slight when compared to advantages ofenabling high-speed operation at significantly reduced clock rates. Thecombinatorial logics are operable to ensure proper implementation of theequations that enable the representation of a present sample in terms ofsamples 1 or 2 samples away. For example, the look-ahead transformationdescribed above shows the implementation where a present sample may bemade using samples that are at least two samples away. Those personshaving skill in the art will appreciate that the present invention maybe extended so as to permit the implementation of representing a presentsample by a sample that is any number n samples away.

In addition, the two parallel paths of the 2-parallel implementation ofa 1-tap DFE 1300 are coupled to one another. For example, theintermediate output signal A_(n) from the time delay z⁻² 1321 is alsofed through a time delay z⁻² 1391, from which an output signal A_(n-2)is fed to the combinatorial logic 1370; the intermediate output signalB_(n) from the time delay z⁻² 1322 is also fed through a time delay z⁻²1392, from which an output signal B_(n-2) is also fed to thecombinatorial logic 1370.

In somewhat analogous manner, the intermediate output signal A_(n-1)from the time delay z⁻² 1361 is fed as one of the inputs to thecombinatorial logic 1330; the intermediate output signal B_(n-1) fromthe time delay z⁻² 1362 is fed as one of the inputs to the combinatoriallogic 1330.

It is also noted that the architecture of the embodiment shown in theFIG. 13 may be generalized to any number of taps K, and any arbitrarynumber of parallel processors M. The clock speed will then be reduces bythe factor M, while maintaining operable performance, and the number ofthresholds required will grow as 2^(K). Theoretically speaking, theclock speed may be reduced indefinitely by extending this particularparallel implementation. While the complexity of the combinatoriallogics 1330 and 1370 may be somewhat more involved to implement theincreased number of parallel paths, the benefits of allowing operationat significantly reduced clock rates will be appreciated by thosepersons having skill in the art. The complexity of the overall systemgrows roughly as M2^(K). Again, it is also noted that the comparatorthresholds may be set to any desired values as required or desired forvarious applications.

However, in one embodiment, if the thresholds are sorted in increasedorder, the operation done by the comparators may be viewed as being a“non-linear thermometer code” encoder. The non-linearity stems from thefact that, in general, the thresholds are not evenly spaced. Toaccomplish the non-linear mapping, a look up table storing thenon-linear mapping, stored in memory that may be Random Access Memory(RAM), could be used. The output of the look up table would then need tobe “reverse sorted” to compensate for the sorting operation performed onthe thresholds. The combinatorial logics 1330 and 1370 may be employedthat is operable to undo this sorting of the thresholds. The combinedoperation of this non-linear mapping, in conjunction with the operationof the combinatorial logic, by re-ordering the thresholds back to theiroriginal ordering, may be used in this and in other embodiments as well.

FIG. 14 is a system diagram illustrating an embodiment of a DSP basedde-serializer/receiver 1400 that is built according to the presentinvention. Serial input data 1410 is fed simultaneously to a number ofPGAs, shown as a PGA 1421, a PGA 1422, a PGA 1423, . . . , and a PGA1429. The outputs of each of the PGAs form channels for the serial inputdata 1410, after undergoing any gain adjustment using the PGAs1421-1429. The output of each of these PGAs is fed to an ADC where theserial data is sampled using a number of ADCs, shown as an ADC 1431, anADC 1432, an ADC 1433, . . . , and an ADC 1439. Together, the ADCs1431-1439 operate to achieve an effective sampling rate of the sum totalof each of the sampling rates of the ADCs 1431-1439. Each of the ADCs1431-1439 operates at substantially the same sampling rate. Additionalintelligence may be employed in various embodiments to accommodate thesituation where some of the ADCs operate at different sampling rates asthe other of the ADCs. The outputs of each of the ADCs are fed to aprecursor filter 1440. The precursor filter 1440 performs the operationof properly creating zero crossings in the now digital samples. Theprecursor filter 1440 also performs pulse shaping to ensure that thepulse is in the proper shape so as to enable timing recovery, as will bedescribed below as well as in other various embodiments. The pulse iseffectively transformed into a shape that allows effective operation ofthe timing recovery.

The outputs of the channels, after they have passed through theprecursor filter 1440, are each fed to a RAM mapper, shown as a RAMmapper 1461, a RAM mapper 1462, a RAM mapper 1463, . . . , and a RAMmapper 1469. The RAM mappers 1461-1469 may include the non-linearmapping of a “non-linear thermometer code”. Other non-linear mappingsmay also be implemented using the RAM mappers 1461-1469 as well withoutdeparting from the scope and spirit of the invention. The channeledoutput from the RAM mappers 1461-1469 are each fed to a switch matrix,shown as a switch matrix 1471, a switch matrix 1472, a switch matrix1473, . . . , and a switch matrix 1479. The switch matrices 1471-1479are each operable to perform the undoing of the mapping performed in theRAM mappers 1461-1469; that is to say, the switch matrices 1471-1479 areoperable to reorder the sorting of the thresholds back to their originalordering for subsequent processing purposes.

The outputs of the switch matrices 1471-1479 are each provided to adecision feedback equalizer 1450 that is implemented in a parallelmanner. The output from the decision feedback equalizer 1450 is providedas parallel digitized data 1430. In addition, the parallel digitizeddata 1430 is also sampled and provided to an adaptation functional block1470. The adaptation functional block 1470, in this embodiment, is shownto provide correction to each of the RAM mappers 1461-1469 and to eachof the switch matrices 1471 based on error information provided by thedecision feedback equalizer 1450.

In addition, the embodiment shown in the FIG. 14 may also be adapted toprovide for timing recovery and automatic gain control (AGC) based onthe sampling of the parallel digitized data 1430, in similar manner asthat shown in the FIG. 11. For example, timing recovery may be employedto provide clock signals that are adapted as necessary, to each of theADCs 1431-1439. In addition, the AGC may be employed to provide gaincontrol signals to the PGAs 1421-1429. Timing recovery may be used toperform adjustment of the sampling times at which the various ADCs1431-1439 may have sampled the incoming serial input data 1410. Forexample, the ADCs 1431-1439 may not operate ideally and may sample theserial input data 1410 at non-uniformly spaced times. To compensate andcorrect for this deficiency in a non-ideal array of ADCs, timingrecovery may be used to adjust the time at which the ADCs effectivelysample the serial input data 1410; more precise clock signals may beprovided to the ADCs via timing recovery as well. AGC would be operableto provide input to the PGAs 1421-1429 to ensure that the gain of theserial input data 1410 is appropriate for the particular data type,channel response, and application context. The gain of the variouschannels into which the serial input data 1410 is partitioned, afterhaving passed through the PGAs 1421-1429, may then be appropriatelyadjusted.

FIG. 15 is a system diagram illustrating an embodiment of a DSP basedSERDES 1500 that is built according to the present invention. The FIG.15 shows a top-level block diagram of the operation of a SERDESaccording to the present invention.

Input data 1510 is fed to a single PGA 1510, where any necessary gainadjustment of the input data 1510 may be performed. In alternativeembodiments, multiple PGAs may be employed in place of the PGA 1510, asdescribed in many of the other various embodiments of the presentinvention. The output of the PGA 1510 is simultaneously fed to a numberof ADCs, shown as an ADC0 1531, an ADC1 1532, an ADC2 1533, . . . , andan ADCn 1539, where it is digitally sampled. The outputs of each of theADCs form channels for the serial input data 1510. The sampling of theADCs 1531-1539 may be adapted to be performed at delayed times. Ifdesired, each of the ADC 1531-1539 covers a different portion of a cycleof the input data 1510. Together, the ADCs 1531-1539 operate to achievean effective sampling rate of the sum total of each of the samplingrates of the ADCs 1531-1539. Each of the ADCs 1531-1539 operates atsubstantially the same sampling rate. Additional intelligence may beemployed in various embodiments to accommodate the situation where someof the ADCs operate at different sampling rates as the other of theADCs.

The outputs of each of the ADCs are fed to a re-synchronizationfunctional block 1540. The re-synchronization functional block 1540 isoperable to synchronize the outputs of all the ADCs in the interleavedarray so that the DSP can operate with a single clock. As a result ofthe interleaved operation, each ADC outputs its samples at a differenttime instant. The re-synchronization functional block 1540 outputs allsamples at the transitions of a single clock, which is the same clockused to operate the DSP.

The channels coming out of the re-synchronization functional block 1540are fed into a feed forward equalizer (FFE) 1545, from which thechanneled outputs are fed to a decision feedback equalizer (DFE) 1550.The DFE 1550 provides information concerning slicer error and decisionto an adaptation functional block 1585. The adaptation functional block1585 is operable to perform PGA adaptation 1586 and ADC adaptation 1587.The PGA adaptation 1586 is operable to provide control to the PGA 1520.In addition, the ADC adaptation 1587 is operable to provide timingrecovery 1589 to the ADCs 1531-1539. The timing recovery 1589 may beperformed individually for each of the ADCs 1531-1539, as shown by theindividual timing recovery functional blocks, including a timingrecovery 0 functional block 1590, a timing recovery 1 functional block1591, a timing recovery 2 functional block 1592, . . . , and a timingrecovery n functional block 1599. The timing recovery 1589 is fed to aclock generator functional block 1588 whose output may be fedindividually to the ADCs 1531-1539.

FIG. 16 is a system diagram illustrating another embodiment of a DSPbased SERDES 1600 that is built according to the present invention. TheFIG. 16 also shows a top-level block diagram of the operation of aSERDES according to the present invention.

Input data 1610 is fed simultaneously to a number of programmable gainamplifiers (PGAs), shown as a PGA0 1621, a PGA1 1622, a PGA2 1623, . . ., and a PGAn 1629. The outputs of each of the PGAs form channels for theserial input data 1610, after undergoing any gain adjustment using thePGAs 1621-1629. The output of each of these PGAs is fed to an ADC wherethe serial data is sampled using a number of ADCs, shown as an ADC01631, an ADC1 1632, an ADC2 1633, . . . , and an ADCn 1639. The samplingof the ADCs 1631-1639 may be adapted to be performed at delayed times.If desired, each of the ADC 1631-1639 covers a different portion of acycle of the input data 1610. Together, the ADCs 1631-1639 operate toachieve an effective sampling rate of the sum total of each of thesampling rates of the ADCs 1631-1639. If desired, each of the ADCs1631-1639 operates at substantially the same sampling rate. Additionalintelligence may be employed in various embodiments to accommodate thesituation where some of the ADCs operate at different sampling rates asthe other of the ADCs. The outputs of each of the ADCs are fed to are-synchronization functional block 1640.

The channeled outputs of the re-synchronization functional block 1640are fed along a path in which a summer is placed, followed by a timedelay z⁻¹. In addition, each of the channeled paths is coupled toanother of the channeled paths. A scaled version of each of thechanneled paths is added in the summers to the channel below it, exceptfor the bottom-most channel, whose scaled version is added to thetop-most channel after having passed through a time delay z⁻¹ 1679. Thescaling factor employed in this embodiment is shown as γ, and thosepersons having skill in the art will appreciate that any other factormay be used to scale the channels before they are added to anotherchannel.

For example, the top-most channel is fed to a summer that receives aγ-scaled and delayed (via the time delay z⁻¹ 1679) version of thebottom-most channel, and it is then passed to a time delay z⁻¹ 1671,before being fed to a decision feedback equalizer 1650. The 2^(nd)channel from the top is fed to a summer that receives a γ-scaled versionof the top channel, and it is then passed to a time delay z⁻¹ 1672,before it is fed to the decision feedback equalizer 1650; the 3^(rd)channel from the top is fed to a summer that receives a γ-scaled versionof the 2^(nd) channel from the top, and it is then passed to a timedelay z⁻¹ 1673, before it is fed to the decision feedback equalizer1650, whose output is provided to a de-scrambler and interface. Thiscontinues for each of the channels within the embodiment shown in theFIG. 16.

The decision feedback equalizer 1650 provides information concerningslicer error and decision to an adaptation functional block 1685. Theadaptation functional block 1685 is operable to perform PGA adaptation1686 and ADC adaptation 1687. The PGA adaptation 1686 is operable toprovide individual control to each of the PGAs 1621-1629, as shown bythe individual PGA adaptation functional blocks, including a PGA0functional block 1680, a PGA1 functional block 1681, a PGA2 functionalblock 1682, . . . , and a PGAn functional block 1689. Analogously, theADC adaptation 1687 is operable to provide individual control to each ofthe ADCs 1631-1639, as shown by the individual timing recoveryfunctional blocks, including a timing recovery 0 functional block 1690,a timing recovery 1 functional block 1691, a timing recovery 2functional block 1692, . . . , and a timing recovery n functional block1699.

FIG. 17 is a system diagram illustrating a 1-slice embodiment ofautomatic gain control (AGC) 1700 that is implemented according to thepresent invention. In this embodiment, a slicer error for the slice X (8bit precision) is provided to a multiplier, where it is combined alsowith a decision for the slicer error X (1 bit precision); both theslicer error and the decision are provided from the same interleave.Both the slicer error for the slice X and the decision for the slice Xare both based on an 800 MHz clock frequency/sampling rate. The outputof the multiplier is also 8 bit precision, and it is fed to a summer.The output of the summer if fed to a time delay z⁻¹ 1710 having a 14 bitprecision. The output of the time delay z⁻¹ 1710 is fed back to thesummer and also passed to time delay z⁻¹²⁸ 1720 having a 14 bitprecision. The clock frequency/sampling rate of the time delay z⁻¹²⁸1720 is 6.25 MHz. The 6.25 MHz clock is fed to both the time delay z⁻¹1710 and the time delay z⁻¹²⁸ 1720. The ratio of the clock frequencies800 MHz/6.25 MHz is 128, thereby requiring the time delay z⁻¹²⁸ 1720.Between the time delay z⁻¹ 1710 and the time delay z⁻¹²⁸ 1720, anaccumulate and dump operation is performed where the signal in the timedelay z⁻¹ 1710 is sub-sampled by 128. A 5 bit gain control signal isprovided as output from the time delay z⁻¹²⁸ 1720.

The control signal, generated by the AGC 1700, may be employed in any ofthe various embodiments to perform adaptation/compensation of a singleAGC, or an array of AGCs, according to the present invention. The FIG.17 shows just one embodiment where such adaptation/compensation may beperformed. Depending on the ratios of the two clock frequencies that areto be interfaced, the ratios of the time delays may be appropriatelyadjusted. The FIG. 17 shows a clock frequency ration of 128, but thosepersons having skill in the art will appreciate that other clockfrequency ratios may also be employed. In addition, varying degrees ofdigital precision may also be employed without departing from the scopeand spirit of the invention. From certain perspectives, FIG. 17 may beviewed as being an implementation of a least means square (LMS)equalizer using a 1-tap method.

FIG. 18 is a system diagram illustrating a 1-slice embodiment of timingrecovery 1800 that is implemented according to the present invention. Inthis embodiment, a slicer error for the slice X (8 bit precision) isprovided to a multiplier, where it is combined also with a decision forthe slicer error X (1 bit precision); both the slicer error and thedecision are provided from different interleaves. It can be shown thatthe averaged value of the product of the decision and the delayed slicererror, as computed by this circuit, is an estimator of the precursor ofthe channel response. The phase locked loop of FIG. 18 forces thesampling phase to a value such that the precursor is zero, in otherwords, the sampling phase is determined by the zero crossing of theprecursor of the channel response. Both the slicer error for the slice Xand the decision for the slice X are both based on an 800 MHz clockfrequency/sampling rate. The output of the multiplier is also 8 bitprecision, and it is fed to a summer. The output of the summer if fed toa time delay z⁻¹ 1810 having a 12 bit precision. The output of the timedelay z⁻¹ 1810 is fed back to the summer and also passed to time delayz⁻³² 1820 having a 12 bit precision. The clock frequency/sampling rateof the time delay z⁻³² 1820 is 25 MHz. The 25 MHz clock is fed to boththe time delay z⁻¹ 1810 and the time delay z⁻³² 1820. The ratio of theclock frequencies 800 MHz/25 MHz is 32, thereby requiring the time delayz⁻³² 1820. Between the time delay z⁻¹ 1810 and the time delay z⁻³² 1820,an accumulate and dump operation is performed where the signal in thetime delay z⁻¹ 1810 is sub-sampled by 32. A proportional path signal isprovided as output from the time delay z⁻² 1820 to a second summer.

The proportional path signal is also provided to a summer in an integralpath as well (top right hand side of FIG. 18). The output from thesummer is passed through a frequency register/time delay z⁻³² 1830having 20 bit precision. The output of the time delay z⁻³² 1830 is fedback to the summer, where it is again combined with the proportionalpath signal, and it is also provided to a multiplier where it is scaledby an integral path signal shown as 2⁻⁸; the output of the multiplier isprovided to the second summer whose output is fed down to a multiplierwhere it is scaled by a signal shown as 2⁻⁵; this top right hand cornerof the FIG. 18 may be viewed as being a 2^(nd) order P+I(proportional+integral) phase locked loop (PLL). The proportionalcontrol is provided by the signal shown as 2⁻⁵. The output of thismultiplier is fed to a numerically controlled oscillator (NCO) 1850. TheNCO 1850 includes a summer whose output is fed to a time delay z⁻³² 1840having 18 bit precision. The output of the time delay z⁻³² 1840 is alsofed back to the summer within the NCO 1850, and the output of the timedelay z⁻³² 1840 also serves as the output of the NCO 1850. The bottomright hand corner of the FIG. 18, including the NCO 1850 may be viewedas including an integrator that is permitted to overflow to provide fortiming recovery control. The output of the timing recovery 1800 is aphase control signal of 5 bit precision.

The phase control signal, generated by the timing recovery 1800, may beemployed in any of the various embodiments to performadaptation/compensation of a single ADC, or an array of ADCs, accordingto the present invention. The FIG. 18 shows just one embodiment wheresuch adaptation/compensation may be performed. Depending on the ratiosof the two clock frequencies that are to be interfaced, the ratios ofthe time delays may be appropriately adjusted. The FIG. 18 shows a clockfrequency ratio of 32, but those persons having skill in the art willappreciate that other clock frequency ratios may also be employed. Inaddition, varying degrees of digital precision may also be employedwithout departing from the scope and spirit of the invention.

FIG. 19 is a system diagram illustrating an embodiment of a scrambler1900 that is employed according to the present invention. The scrambleris operable to receive multiple inputs, shown generically as x_(n),x_(n-1), x_(n-2), and x_(n-3). Those persons having skill in the artwill recognize that any number of inputs may be used, and not merely thefour illustrated in the FIG. 19. The inputs are fed into combinatoriallogic 1910, whose outputs are fed to a number n of time delays, shown atthe top as a time delay z⁻¹ 1921, . . . , and a time delay z⁻¹ 1931.Similarly, there is a number n of time delays for the other threechannels as well. A number of taps, as determined from informationstored in a shift register, are selected and fed back to thecombinatorial logic 1910. In addition, the output signals from thecombinatorial logic 1910 are all fed to a time delay z⁻¹ 1920, fromwhich the outputs y_(n), y_(n-1), y_(n-2), and y_(n-3) are generated.The clock rate is 800 MHz in this particular embodiment, but other clockrates may also be employed as understood by those persons having skillin the art.

The scrambler 1900 is employed to ensure a random looking data stream,as will be understood by those persons having skill in the art. Ifdesired, the same polynomial as that used in 1000BaseT Ethernet may beemployed, as used on the slave side as follows:g _(s)(x)=1+x ²⁰ +x ³³

For simplicity, this may be implemented as a self-synchronizingscrambler. The self-synchronizing scrambler may be viewed as beingessentially a recursive filter (in modulo 2 arithmetic), and it can beparallelized using a number of transformations including a look-aheadtransformation.

FIG. 20 is a system diagram illustrating an embodiment of a de-scrambler2000 that is employed according to the present invention. Thede-scrambler 2000 may be viewed as the entity that performs thede-scrambling of the scrambling performed by the scrambler 1900. Thede-scrambler 2000 is operable to receive multiple inputs, showngenerically as x_(n), x_(n-1), x_(n-2), and x_(n-3). Those personshaving skill in the art will recognize that any number of inputs may beused, and not merely the four illustrated in the FIG. 20. The inputs arefed into channels having a number n of time delays. The top channel, forthe input of x_(n), is fed into a time delay z⁻¹ 2021, . . . , and atime delay z⁻¹ 2031. The other three channels in this embodiment arehandled similarly. As determined from information stored in a shiftregister, the selected taps indicate which taps are to be fed into acombinatorial logic 2010. In addition, the output signals from thecombinatorial logic 2010 are each fed to individual time delays, shownas a time delay z⁻¹ 2041, a time delay z⁻¹ 2042, a time delay z⁻¹ 2043,and a time delay z⁻¹ 2044, from which the outputs y_(n), y_(n-1),y_(n-2), and y_(n-3) are generated. The clock rate is 800 MHz in thisparticular embodiment, but other clock rates may also be employed asunderstood by those persons having skill in the art. The outputs y_(n),y_(n-1), y_(n-2), and y_(n-3) in the FIG. 20 represent the un-scrambledversion of the inputs outputs x_(n), x_(n-1), x_(n-2), and x_(n-3) ofthe FIG. 19.

In addition, the present invention is operable to employ a start-upcontroller in various embodiments. A start-up controller is a statemachine that sequences the control signals during start-up to facilitateconvergence of various components including DFE, AGC, and timingrecovery. The start-up controller is operable to run at relatively lowclock speeds, so as not to contribute significantly to power dissipationin the overall system. For example, a nominal clock rate of less than 1MHz would be sufficient in most instances.

FIG. 21 is a functional block diagram illustrating an embodiment of aDSP based SERDES de-serializer method 2100 that is performed accordingto the present invention. In a block 2110, a serial/analog signal isreceived. Then, in a block 2120, analog to digital conversion isperformed on the serial/analog signal that is received in the block2110. After any analysis of the now-digitized signal, any necessaryadaptation/compensation is performed in a block 2130. Before performingany necessary adaptation/compensation, as shown in the block 2130, it isfirst determined whether any adaptation/compensation needs to beperformed at all. It may be that no adaptation/compensation need beperformed at all, and the present invention is operable to accommodatethis contingency as well.

FIG. 22 is a functional block diagram illustrating another embodiment ofa DSP based SERDES de-serializer method 2200 that is performed accordingto the present invention. In a block 2210, all possible input parametersthat may affect an incoming serial analog data signal are identified.The identification of the possible input parameters 2210 includesidentification of the input signal type 2213. In some embodiments, theidentification of the possible input parameters 2210 includesidentifying the coding types 2214 by which an input signal was encoded,the channel response 2212 of a communication link over which the inputsignal has come, as well as any other parameters 2219. Again, within thecontext of data communications applications, certain DSP-basedtechniques may be optimized to discern various information concerningthe input signal and the communication channel over which the inputsignal has been transmitted.

Then, based upon this knowledge or foreknowledge of the input signal,and the communication channel over which the input signal has come, allpossible values of feedback signal (that providesadaptation/compensation) are pre-computed in a block 2220. Then, in ablock 2230, the adaptation/compensation is applied to the appropriateblocks via a feedback signal. The feedback signal may be applied to oneor more ADCs (say to an ADC array) as shown in a functional block 2231,to one or more PGAs as shown in a functional block 2232. The feedbacksignal may be fed to a device residing before an ADC that performsanalog to digital conversion 2233, or to a device residing after the ADCthat performs analog to digital conversion 2234. Moreover, parallelbased techniques may be employed according to the present invention todeliver this feedback signal, as shown in a functional block 2235.

Then, based upon this knowledge or foreknowledge of the input signal,and the communication channel over which the input signal has come, allpossible values of adaptation/compensation may be pre-computed in ablock 2240. Then, the adaptation/compensation is performed directlyusing a DSP, as shown in a functional block 2250.

In addition, it is also noted that some of the adaptation/compensationmay be performed, in part, using a DSP and also performed, in part,using a device to which a feedback signal is provided. The presentinvention is adaptable to perform hybrid adaptation/compensation.

FIG. 23 is a functional block diagram illustrating another embodiment ofa DSP based SERDES de-serializer method 2300 that is performed accordingto the present invention. In a block 2310, a serial/analog signal isreceived. Then, in a block 2320, the serial/analog signal is partitionedusing a number of ADC channels. An ADC array, having a number of ADCs,is used to multiplex the various channels into which the signal ispartitioned.

Then, in a block 2330, any necessary adaptation/compensation isperformed. The necessary adaptation/compensation may be performed afterone or more ADCs, as shown in a functional block 2334, and it may beperformed individually to all of the devices, as shown in a functionalblock 2350. In the ADC array context, the necessaryadaptation/compensation is performed on an ADC basis as shown in afunctional block 2351. Alternatively, the necessaryadaptation/compensation may also be performed before any ADCs, as shownin a functional block 2332.

The present invention is operable to perform the DSP based SERDESde-serializer method 2300 in a manner that any necessaryadaptation/compensation may be performed to any number of devices, suchas one a to one or more PGA basis (as shown in a functional block 2352),and it may also be performed individually to any other type of device2359. The PGA basis 2352 may be performed using AGCs in certainembodiments. Alternatively, parallel based techniques 2360 may also beperformed in doing the necessary adaptation/compensation. In addition,the necessary adaptation/compensation may also be performed jointly toall devices as if they are they were a single entity or device. This maybe performed to all ADCs 2341, to all PGAs 2342 (perhaps using a numberof AGCs as shown in a functional block 243), or alternatively to anyother number of devices 2349 that are configured to operate as a singleentity.

FIG. 24 is a functional block diagram illustrating another embodiment ofa DSP based SERDES de-serializer method 2400 that is performed accordingto the present invention. In a block 2410, a serial/analog signal isreceived. Then, in a block 2420, the analog/serial signal is partitionedinto a number of channels prior to performing any analog to digitalconversion (prior to any ADCs) using analog circuitry. Then, in a block2430, the analog to digital conversion is performed on each channelhaving one portion of the now-partitioned serial/analog signal.

In a block 2440, it is determined whether there is any necessaryadaptation/compensation control needs to be performed using a DSP, afteranalyzing the now digital data in each of the various channels. Incertain embodiments, the necessary adaptation/compensation control maybe determined whether it should or can be performed before or after theanalog to digital conversion of the serial/analog, channeled data. Then,in a block 2460, the compensation/determination is performed usinganalog circuitry that is situated before the ADCs of the variouschannels. The control signals, to each of the various ADCs, are passedfrom the DSP to the analog circuitry. If desired, the control to theanalog circuitry is delivered using parallel based techniques.

Alternatively, the compensation/determination is performed using a DSP,as shown in a block 2450; the compensation/determination is performed byperforming mathematical manipulation of the now-digital data. Inaddition, any number of multiple DSPs may also be employed, as shown ina functional block 2451.

FIG. 25 is a functional block diagram illustrating an embodiment of aDSP based SERDES training/operating method that is performed accordingto the present invention. In a block 2510, a system is powered up. Thesystem includes at least one DSP based SERDES. In a block 2520, the DSPbased SERDES is trained. The training includes calculating thecoefficients of any equalization requirements, accommodating any ADCs,PGAs, or other circuitries that are employed in the system to deal withmany of the deficiencies that may be present, as described above in manyof the various embodiments, including gain, phase, offset, timing, andother deficiencies. Once the system is trained, the system may runindefinitely, for days, months, years, and so on. As shown in a block2530, the DSP based SERDES is in an operation mode offering veryhigh-speed operation of a SERDES that benefits from the advantages ofDSP based parallel techniques in any of the embodiments described aboveand within the scope and spirit of the invention.

Then, once the DSP based SERDES is in an operational mode, any number ofevents and/or conditions may occur that would initiate a re-training ofthe DSP based SERDES. If no such event and/or condition occurs, then theDSP based SERDES will simply run indefinitely, as mentioned above.However, some situations necessitate the re-training of the DSP basedSERDES to achieve desirable operation once again.

One such example that may be used to initiate the retraining of the DSPbased SERDES includes a power loss in the system, as shown in afunctional block 2551. This power loss may be determined as having beenfor a predetermined duration, as indicated in a functional block 2552.If desired, brief or nearly instantaneous power losses may be ignored,as desired in certain embodiments. Alternatively, after power losses ofcertain duration, an abbreviated re-training may be performed. In suchsituations, those system operational parameters that have a lowlikelihood of changing may be ignored, yet those parameters that aremore volatile may be re-calculated, and those parts of the system maythen be retrained, as shown in a functional block 2550. Then, once theDSP based SERDES is re-trained, the method returns to the operating modeof the DSP based SERDES, as shown in the functional block 2530.Alternatively, the method 2500 may end. The ending may be usercontrolled, or as controlled by the DSP based SERDES.

Another such example that may be used to initiate the retaining of theDSP based SERDES includes a loss of the coefficients of an equalizerthat is employed in the system, as shown in a functional block 2561. Anynumber of techniques may be employed to detect a loss of thecoefficients of any equalizer. Then, once the DSP based SERDES isre-trained, the method returns to the operating mode of the DSP basedSERDES, as shown in the functional block 2530. Alternatively, the method2500 may end. The ending may be user controlled, or as controlled by theDSP based SERDES.

Another such example that may be used to initiate the retraining of theDSP based SERDES includes a detection of an error in the system, asshown in a functional block 2571. Any number of error detectiontechniques, as understood by those persons having skill in the art, maybe employed to detect an error in the system. The error detection mayinclude degraded system performance (functional block 2572), where thereis evidence of some change in the system that has contributed tocompromised performance. Another situation is where the equalizer ceasesto provide proper operation because the equalizer has diverged(functional block 2573), and it no longer converges or properlyoperates. Then, once the DSP based SERDES is re-trained, the methodreturns to the operating mode of the DSP based SERDES, as shown in thefunctional block 2530. Alternatively, the method 2500 may end. Theending may be user controlled, or as controlled by the DSP based SERDES.

Moreover, any other event and/or condition (functional block 2581) maybe used to initiate the re-training of the DSP based SERDES. Examples ofsome other events and/or conditions include seemingly changed operatingconditions, including environmental changes (including temperature,humidity) that have substantially altered the performance of the overallsystem.

FIG. 26 is a diagram illustrating functionality 2600 that may besupported in any of the various embodiments of a DSP based SERDES thatis built according to the present invention. The present invention isoperable to perform a variety of decoding operations 2630 on digitaldata that is generated within any of the various embodiments describedherein. For example, this decoding may be performed using Viterbidecoding 2631. The Viterbi decoding itself may also perform partialresponse maximum likelihood (PRML) decoding 2632. The decodingoperations 2630 may also include decoding ISI 2641; the ISI itself maybe generated from a channel that has been shaped by a partial response2642 that is not a perfectly accurate characterization of the channel'sresponse.

Moreover, it is noted that the SERDES based interfacing between devicesmay be performed using alternatively means as well, as shown by theconnectivity options between devices 2670. For example, there may beother possibilities in which at least two devices may be communicativelycoupled that may benefit from the present invention. Two devices may becommunicatively coupled via twisted pair cabling 2671, coaxial cabling2672, and/or twin-ax cabling 2673, among others.

Generically speaking, the compensation that may be performed accordingto the present invention includes a number of compensation types, manyof which have been described herein. The present invention is able tocompensate for various types of errors 2610, including ISI 2611, andattenuation 2650. The attenuation 2650 may be generated due to thevariations among various channels (CHs) 2651, and it may be compensatedusing one or more PGAs and/or one or more ADCs 2652. Those personshaving skill in the art will appreciate how the use of such devices maybe used to compensate for such degradation of attenuation 2650.

Moreover, the present invention is operable to compensate for varioustypes of crosstalk using crosstalk cancellation 2660. The crosstalkcancellation 2660 may be employed using a crosstalk canceller within anyof the various transmitters, receivers, and/or transceivers that may bearranged and employed according to the present invention. The crosstalkcancellation 2660 may be performed to overcome the effects of NEXT 2662and/or FEXT 2661.

In addition, various offsets mismatches 2620 of the differentinterleaved paths may need compensation, and the present invention isoperable to overcome these effects as well. These offset mismatches 2620may result due to non-uniformities of various interleaves 2621 in thevarious embodiments of the present invention. The non-uniformities ofvarious interleaves 2621 may result in fixed pattern noise that must beaddressed and may be substantially eliminated using the DSP compensationand correction techniques performed according to the present invention.

Various embodiments and aspects of the present invention have beendescribed above. Some of the aspects are geared towards datacommunications applications. Those persons having skill in the art willrecognize the extendibility of the present invention to any applicationwhere operational parameters and knowledge of the type of an incomingsignal, the channel type, the channel response and other information maybe discerned may also benefit from the various aspects of the presentinvention.

In view of the above detailed description of the invention andassociated drawings, other modifications and variations will now becomeapparent to those skilled in the art. It should also be apparent thatsuch other modifications and variations may be effected withoutdeparting from the spirit and scope of the invention.

1. A communication device, comprising: a compensation circuitryimplemented to process a first signal thereby generating a secondsignal; an analog to digital converter (ADC) implemented to sample thesecond signal to generate digital samples there from; and a digitalsignal processor (DSP) implemented to receive the digital samples,wherein: the DSP implemented to determine adaptively at least onecompensation operation to be performed on the digital samples so thatthe digital samples may be properly characterized to extract digitaldata contained therein; and at least one module, within thecommunication device and coupled to the DSP, implemented to perform theat least one compensation operation as directed by the DSP; and the DSPimplemented to determine adaptively at least one additional compensationoperation to be performed on the first signal by the compensationcircuitry.
 2. The communication device of claim 1, wherein: the at leastone module within communication device is the ADC.
 3. The communicationdevice of claim 1, wherein: the compensation circuitry including aprogrammable gain amplifier (PGA).
 4. The communication device of claim1, wherein: the DSP implemented to determine adaptively at least oneadditional compensation operation to be performed on the digitalsamples; and the DSP implemented to perform the at least one additionalcompensation operation.
 5. The communication device of claim 1, wherein:the compensation circuitry including a plurality of programmable gainamplifiers (PGAs).
 6. The communication device of claim 1, wherein: thecompensation circuitry including a programmable gain amplifier (PGA)whose operation is governed in accordance with an automatic gain control(AGC).
 7. The communication device of claim 1, wherein: the ADC is oneADC of a plurality of ADCs within the communication device; each ADC ofthe plurality of ADCs is coupled to the DSP; each ADC of the pluralityof ADCs implemented to perform sampling of the second signal; the atleast one compensation operation is one compensation operation of aplurality of compensation operations; the DSP implemented to determineadaptively the plurality of compensation operations to be performed onthe digital samples; and the plurality of compensation operationsperformed on the digital samples by each ADC of the plurality of ADCs.8. The communication device of claim 1, further comprising: at least oneadditional module implemented to process the digital samples before thedigital samples received by the DSP; and the DSP implemented todetermine adaptively at least one additional compensation operation tobe performed on the digital samples by the at least one additionalmodule.
 9. The communication device of claim 1, wherein: the DSPincluding at least one of a feedback equalizer and a decision feedbackequalizer implemented to assist in determining the at least onecompensation operation.
 10. The communication device of claim 1,wherein: the ADC and the DSP are implemented within an integratedcircuit.
 11. A communication device, comprising: a compensationcircuitry implemented to process a first signal thereby generating asecond signal; an analog to digital converter (ADC) implemented tosample the second signal to generate digital samples there from; and adigital signal processor (DSP) implemented to receive the digitalsamples, wherein: the DSP implemented to determine adaptively a firstcompensation operation to be performed on the first signal by thecompensation circuitry and a second compensation operation to beperformed on the digital samples so that the digital samples may beproperly characterized to extract digital data contained therein. 12.The communication device of claim 11, wherein: the DSP implemented todetermine adaptively a third compensation operation to adjust at leastone operational parameter of the ADC so that the digital samples may beproperly characterized to extract digital data contained therein. 13.The communication device of claim 11, wherein: the DSP implemented todetermine adaptively a third compensation operation to adjust at leastone operational parameter of the ADC so that the digital samples may beproperly characterized to extract digital data contained therein; andthe at least one operational parameter of the ADC is an ADC phasemismatch, an ADC gain mismatch, or an ADC offset mismatch.
 14. Thecommunication device of claim 11, wherein: the DSP implemented toperform the second compensation operation on the digital samples so thatthe digital samples may be properly characterized to extract digitaldata contained therein.
 15. The communication device of claim 11,wherein: the ADC and the DSP are implemented within an integratedcircuit.
 16. A communication device, comprising: an analog to digitalconverter (ADC) implemented to sample a signal to generate digitalsamples there from; and a digital signal processor (DSP) implemented toreceive the digital samples, wherein: the DSP implemented to determineadaptively a first compensation operation to be performed on the signalby a compensation circuitry and a second compensation operation toadjust at least one operational parameter of the ADC so that the digitalsamples may be properly characterized to extract digital data containedtherein.
 17. The communication device of claim 16, wherein: the signalis a first signal; and the compensation circuitry implemented to processa second signal thereby generating the first signal.
 18. Thecommunication device of claim 16, wherein: the signal is a first signal;the compensation circuitry implemented to process a second signalthereby generating the first signal; and the DSP implemented todetermine adaptively a third compensation operation to be performed onthe first signal by the compensation circuitry so that the digitalsamples may be properly characterized to extract digital data containedtherein.
 19. The communication device of claim 16, wherein: the DSPincluding at least one of a feedback equalizer and a decision feedbackequalizer implemented to assist in determining at least one of the firstcompensation operation and the second first compensation operation. 20.The communication device of claim 16, wherein: the ADC and the DSP areimplemented within an integrated circuit.